This invention relates generally to wind turbines, and more specifically to repair of pitch control components.
At least some known wind turbines have pitch control systems comprised of a bearing coupled between a blade and a hub with a pitch motor positioning the blade attached to the bearing. The bearing may include a row of teeth that engage a gear of the motor. The motor's gear turns or pitches the blade by interacting with the teeth on the pitch bearing. Over time some of the bearing's teeth can become damaged, worn or may break off. Current known solutions to repair a pitch control component require the removal of the affected blade or the entire rotor. In either case, a large crane is required for removal, and cranes of this type are costly. In addition, the wind turbine is taken off-line until the repairs can be completed.
In some wind turbines, the blades are up to 60 meters in length, but may be designed to be up to 100 meters, so removal to change a damaged pitch control system can be costly and time consuming. Other known wind turbines are offshore, requiring extensive equipment to remove a blade and replace the pitch control system components. Wind turbines hub heights can be over 120 meters and in high winds, making it dangerous for workers to be on the wind turbines.
A malfunctioning pitch control system can also cause a blade to move out of a pitch setting such that the blades of the wind turbine asymmetrically load the hub and rotor shaft. If the rotor begins to move within the stator due to the asymmetric loading, there is a possibility of the rotor contacting the stator, for example, in direct drive application with the turbine rotor being attached directly to the generator. An electrical transient can occur if the rotor and stator contact, and the wind turbine may then have to be taken off-line.